Various products have been designed with the goal of eliminating unwanted sounds or “auditory pollution” so that users can listen to a desired audio source or substantially eliminate noises from surrounding activities. More and more objects, events, and situations continue to generate auditory information of various kinds. Some of this auditory information is welcomed, but much of it may be perceived as distracting, unwanted, and irrelevant. One's natural ability to focus on certain sounds and ignore others is continually challenged and may decrease with age.
Various types of noise cancelling headphones and hearing aid devices allow users some control or influence over their auditory environment. Noise cancelling systems usually cancel or enhance the overall sound field, but do not distinguish between various types of sounds or sound events. In other words, the cancellation or enhancement is not selective and cannot be finely tuned by the user. While some hearing aid devices can be tuned for use in certain environments and settings, those systems often do not provide desired flexibility and fine grained dynamic control to influence the user's auditory environment. Similarly, in-ear monitoring devices, such as worn by artists on stage, may be fed with a very specific sound mix prepared by a monitor mixing engineer. However, this is a manual process, and uses only additive mixing.